If the PWM is not enabled the backlight initially should not be enabled
either if we have booted with DT and there is a phandle pointing to the
backlight node.

The patch extends the checks to decide if we should keep the backlight off
initially.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>